The invention relates to a valve for controlling liquids.
From European Patent Disclosure EP 0 477 400 A1, such a valve is already known which is actuatable via a piezoelectric actuator. This known valve has an arrangement for a travel transformer of the piezoelectric actuator, effective in the stroke direction, in which the deflection of the piezoelectric actuator is transmitted via a hydraulic chamber that functions as a hydraulic step-up means or coupling and tolerance compensation element.
The hydraulic chamber encloses a common compensation volume between two pistons defining this chamber, of which one piston is embodied with a smaller diameter and is connected to a valve member to be triggered, and the other piston is embodied with a larger diameter and is connected to the piezoelectric actuator. The hydraulic chamber is fastened between the two pistons in such a way that the actuating piston of the valve member, which piston is retained in its position of repose by means of one or more springs relative to a predetermined position, executes a stroke that is increased by the step-up ratio of the piston diameter when the larger piston is moved a certain travel distance by the piezoelectric actuator. The valve member, piston and piezoelectric actuator are located one after the other on a common axis. Via the compensation volume of the hydraulic chamber, tolerances caused by temperature gradients in the component or different coefficients of thermal expansion of the materials used and possible settling effects can be compensated for without causing a change in position of the valve member to be triggered.
The hydraulic coupler requires a system pressure, which drops because of leakage if adequate refilling with hydraulic liquid is not done.
In the industry, in common rail injectors, versions are known in which the system pressure is expediently generated in the valve itself, and a constant system pressure is assured even upon system starting. To that end, hydraulic liquid is drawn from a high-pressure region of the fuel to be controlled and delivered to the low-pressure region at the system pressure. This is done with the aid of leakage gaps, which are defined by leakage or filling pins.
However, if the pressure in the high-pressure region rises, the leakage rate in the system region automatically increases. Under some circumstances, the result is an impermissible high leakage loss from the valve, which severely reduces the efficiency of the system.
The object of the invention is to create a valve for controlling liquids with which the leakage losses at increasing pressure in the high-pressure region are limited.
The valve according to the invention for controlling liquids has the advantage that to generate the minimum leakage rate from the high-pressure region into the low-pressure region at system pressure, a throttle bore is used, and thus the leakage loss at high pressures in the high-pressure region is reduced by multiple times compared with the system pressure supply through a conventional leakage gap or filling pin.
In a simple way, the fundamentally different physical flow effects between the turbulent flow through a throttle bore and the laminar gap flow around a filling pin are utilized to realize the filling of the low-pressure region.
Further advantages and advantageous features of the subject of the invention can be learned from the specification, drawing and claims.